This invention relates to flame-retardant polyamides, i.e., polymers having the polycarbonamide group in the main polymer chain. In particular, this invention relates to flame-retardant polyamide fibers for use in flame-retardant carpets. In one of its more specific embodiments, this invention relates to flame-retardant polyamide carpets and process for the preparation thereof.
A number of metal compounds have been reported in the literature as flame retardants for various substrates. By far the most notable prior art compounds are antimony oxide and antimony chloride. Other metal compounds described as fire retardants include phosphates and borates of alkali metals and alkaline earth metals, aluminum hydrate, titanium salts, tin salts, and double salts such as potassium hexafluorozirconate and potassium hexafluorotitanate.
In recent years, much research has been carried out directed to production of flame-retardant carpeting. The following patents indicate the state of this art.
U.S. Pat. No. 3,418,267 to W. F. Busse relates to flame-resistant polyamides and process thereof. The patent dicloses that polyamide resin is made flame retardant by incorporating therein from 5 to 20 percent by weight of an organic halide, e.g., chlorinated biphenyl, which is reactive with the resin only at its pyrolysis temperature and from 3 to 15 percent by weight of an oxide of tin, lead, copper, iron, zinc or antimony.
U.S. Pat. No. 3,663,345 to G. G. Jaisinghani, discloses a fire retardent carpet in which the pile fibers are fixed to the primary backing by a compound comprising a latex binding material combined with an aluminum hydrate.
U.S. Pat. No. 3,719,547, to D. H. Martin et al., described a flame-retardant pile fabric. A fibrous layer composed of combustible filaments or fibers extends from the top surface of a fibrous backing to present a pile surface. A coating of a film-forming halogen-containing polymer and a water-insoluble organo-phophorus compound is applied to and confined essentially to the top surface of the backing. Where the backing is made of a thermoplastic material, a coating of the halogen-containing polymer may be used without the organic-phosphorus compound.
It has been suggested in U.S. Pat. No. 3,956,236, to F. E. Evans et al., that flame resistance of carpets, such as polyamide and polyester carpets, can be increased by adding a synergistic composition comprising a metal salt of certain organic acids, particularly metal salts of hydroxycarboxylic acids, with certain organic acids or their ammonium salts, particularly hydroxycarboxylic acids or their ammonium salts. Also, U.S. Pat. No. 3,943,100, to M. B. Berenbaum et al., describes flame retardants based on certain organic acids, e.g., gallic acid, citric acid, or tartaric acid, or the ammonium, lithium or magnesium salts thereof. Although these patents constitute a major contribution to this art, investigations have been continued to develop an improved flame-retardant carpet wherein the flame retardent polyamide fiber has improved luster and/or improved colorfastness to light when the fiber is dyed.